1. Field of the Invention
The invention relates to a control device, a control method, and a control program, and especially relates to a control device, a control method, and a control program of a fastening tool.
2. Description of Related Art
When fastening a fastening member such as a nut and a bolt by using a nut runner that is a representative example of a fastening tool, it is important to fasten the fastening member with given torque.
For example, Japanese Patent Application Publication No. 6-79552 (JP 6-79552 A) discloses a technology in which a rate of increase of torque per angle, which is set in advance on a torque curve, is measured continuously, and quality of plastic-region fastening of the bolt is determined based on a comparison between maximum torque measured in a fastening process and torque when the fastening is completed.
In general, when a fastening member is fastened by using a fastening tool, the fastening tool is controlled so as to follow a torque curve that is set by an empirical rule in advance. At that time, even for the same target fastening torque, characteristics of reaching the optimum target fastening torque are different depending on differences in rigidity of a fastened member (for example, a rigid body, an intermediate, and a soft body).
The technology described in JP 6-79552 A enables determination of quality of plastic-region fastening of a bolt, but is not able to deal with differences in rigidity of a fastened member. Therefore, there is a room remaining for an improvement of fastening accuracy.